Polyphosphazene polymers containing repeating ##STR3## units in which various substituted and unsubstituted alkoxy, aryloxy, amino and mercapto groups are attached to the phosphorus atom and their method of preparation are described in the prior art as illustrated in the publication "Nitrogen-Phosphorus Compounds", Academic Press, New York, N.Y., 1972 by H. R. Allcock and "Poly(organophosphazenes)", Chemtech, Sept. 19, 1975, by H. R. Allcock and in such U.S. Pat. Nos. 3,515,688; 3,702,833; 3,856,712; 3,974,242; and 4,042,561, the disclosures of which are herein incorporated by reference.
However, none of the aforementioned publications and patents or for that matter, none of the prior art of which applicants are aware, discloses or suggests polyphosphazene copolymers containing cyclic ketal substituents attached to the phosphorus atom or methods of preparing such polymers.